The present invention is directed to a gas burner for externally heating glass bodies, which are rotated relative to the burner on a rotational axis. The burner has a plurality of multi-jet gas port blocks, each of which has a plurality of jets on a front surface arranged around a block axis. The blocks are disposed at a radial distance from said rotational axis and are simultaneously displaceable along the rotational axis. The multi-jet gas blocks are positioned with their block axes extending radially from the rotational axis in different directions with the jets facing the rotational axis. The gas burner is particularly useful for heating glass tubes during the manufacture of preforms for optical glass fibers.
A gas burner, which has a plurality of multi-jet gas port blocks with each block having a plurality of jets on a front surface to surround a block axis with the port blocks being disposed a radial distance from a rotational axis of the workpiece with the block axes extending radially therefrom in different directions and the blocks being simultaneously displaceable along the rotational axis, are known. An example is "gas burner No. 141/16 W-WK-Special" which is disclosed in a sales brochure of Herbert Arnold Co., Weilburg/Lahn, Weilstrasse 21, entitled "Gasbrenner fur Stadtgas - Erdgas - Propangas - Wasserstoffgas", Brennerprospekt 2. This gas burner, in particular, also represents a special development for the light waveguide manufacturing technology.
A standard execution of the gas burner comprises four gas port blocks. A gas burner with which a substrate of workpiece of silica glass can be externally heated to a temperature in the range of 1600.degree. through 2200.degree. C. are required for the manufacture of preforms for light waveguides of glass according to the inside deposition method (see in this regard Telcom Report 6 (1983), Supplement "Nachrichtenubertragung mit Licht", Pages 29-34).